The results show that late sleep timing in healthy adults with a habitual sleep duration of at least 6.5 hours is linked with poorer diet quality, particularly fast food, vegetable and dairy intake, researchers said.

"Our results help us further understand how sleep timing in addition to duration may affect obesity risk," said Kelly Glazer Baron from Northwestern University in the US.

"It is possible that poor dietary behaviours may predispose individuals with late sleep to increased risk of weight gain," said Baron.

Researchers studied 96 healthy adults between the ages of 18 and 50 years with sleep duration of 6.5 hours or more.

The study involved seven days of wrist actigraphy to measure sleep, food diaries to measure caloric intake and dietary patterns, and SenseWear arm band monitoring to measure physical activity.